1. Field of the Invention
The present invention relates to an impeller for use in a centrifugal blower employed by air conditioning equipment and the like, the impeller comprising a hub for receiving a driving torque at a central portion thereof, a shroud of a ring-like shape in plane formed with an opening for air intake at the center thereof and opposed to the hub across a required distance therebetween, and a plurality of vane members interposed between the hub and shroud as circumferentially spaced from one another at required intervals, and more particularly to an impeller adapted to take in air from the air intake 12a of the shroud and to efficiently discharge the air from the impeller.
1. Description of the Related Art
Conventionally, the air conditioners have employed various types of blowers for feeding air to the heat exchangers and the like. A centrifugal blower has been widely used as one of such blowers.
The centrifugal blowers have generally employed an impeller 10 comprising a hub 11 of a circular shape in plan having a protrusion at the center thereof, a shroud 12 of a ring-like shape in plane formed with an opening for air intake 12a and opposed to the hub 11 across a required distance therebetween, and a plurality of vane members 13 interposed between the hub 11 and shroud 12 as circumferentially spaced from one another at required intervals, as shown in FIGS. 1 and 2.
The centrifugal blower is arranged such that a torque is applied to the central portion of the hub 11 for rotating the impeller 10 which, in turn, is allowed to produce an air flow entering the impeller 10 from the air intake 12a of the shroud 12 to be guided by the rotating vane members 13 through gaps between the hub 11 and shroud 12 and out of the outer periphery of the impeller 10.
Various types of vane members 13 have heretofore been developed in many attempts to increase the efficiency of discharging the air from the aforementioned impeller 10 which is adapted to rotate for producing the air flow running thereinto from the air intake 12a to be guided by the rotating vane members 13 through the gaps between the hub 11 and shroud 12 and out of the outer periphery of the impeller 10.
In the conventional impeller as shown in FIG. 3, the vane members 13 are interposed between the hub 11 and the shroud 12 in a manner such that leading edges of the vane members 13 each form an angle .theta. (inlet angle) with a tangent line to an inner circumference defined by the vane members 13, the angle 0 conforming to an inflow angle .phi. of the air flow introduced into the gap between adjacent vane members 13. Each vane member 13 has the inlet angle .theta. at any points of a span between the hub 11 and shroud 12.
Unfortunately, if the impeller 10 with the vane members 13 of such an arrangement is caused to rotate to produce the air flow running into the impeller 10 and through the gaps between the hub 11 and shroud 12 to be discharged from the outer periphery of the impeller 10, the air flow guided by the vane members 13 fails to run in line with the surfaces thereof, thus departing therefrom and hence, the occurrence of eddies results. The eddies interferes with the flow of air to be discharged as guided by the vane members 13 and hence, the efficiency of air discharge is decreased and increased noises are produced during operation.
Furthermore, the conventional impeller 10 is arranged such that the air is drawn through the air intake 12a and guided through the gaps between the hub 11 and shroud 12 to be discharged horizontally from the outer periphery of the impeller 10. Accordingly, the vane members 13 each have an trailing edge portion substantially extended horizontally, as seen in FIGS. 4 and 5.
Unfortunately, in the arrangement adapted for the air flow running into the impeller 10 from the air intake 12a to be discharged horizontally from the outer periphery thereof as guided by the vane members, air streams closer to the shroud 12 with the air intake 12a are reduced in a flow rate as discharged whereas air streams closer to the hub 11 are correspondingly increased in the flow rate as discharged. A difference of the flow rate between the air streams near the shroud 12 and those near the hub 11 results in the occurrence of eddy which, in turn, causes turbulence of the air flow. The turbulent air flow not only leads to an increased noise during operation but also interferes with the flow of air to be discharged as guided by the vane members 13. As a result, the air feeding efficiency is decreased.